1. Field of the Invention
The present invention relates to a die clamping system used in a die cast machine, molding machine, etc., more particularly relates to a die clamping system wherein tie bars are withdrawable.
2. Description of the Related Art
To facilitate the exchange of dies, a die clamping system having withdrawable tie bars hung between a moveable die plate and fixed die plate is known. Japanese Patent Publication (A) No. 2003-334648 disclose a die clamping system having withdrawal cylinders provided at the moveable die plate and withdrawing the tie bars. The piston rods of the withdrawal cylinders are fixed to the tie bars. In this die clamping system, when the moveable die plate is in a die opening position, moving the tie bars to the moveable die plate side by the withdrawal cylinders causes the tie bars to be withdrawn from the fixed die plate. Japanese Patent Publication (A) No. 2005-144802 discloses a technique using withdrawal cylinders the same as those of Japanese Patent Publication (A) No. 2003-334648 as die opening and closing cylinders. Japanese Utility Model Registration No. 2574639 discloses a die clamping system providing the withdrawal cylinders moveable in the withdrawing direction of the tie bars with respect to a link housing and engagement members engaging the link housing and the withdrawal cylinders with each other. By repeatedly alternately operating the withdrawal cylinders and operating the engagement members, it is possible to split the movement of the tie bars by the withdrawal cylinders into two operations and thus make the strokes of the withdrawal cylinders smaller than the amounts of movement of the tie bars during withdrawal.
In the techniques of Japanese Patent Publication (A) No. 2003-334648 and Japanese Patent Publication (A) No. 2005-144802, the tie bars are withdrawn only by the withdrawal cylinders, therefore the withdrawal cylinders require strokes equivalent to the amounts of movement of the tie bars during withdrawal—forcing the withdrawal cylinders to be made large. In the technique of Japanese Utility Model Registration No. 2574639, it is necessary for the withdrawal cylinders to be provided moveable with respect to the die clamping system, causing the configuration to be complicated.